The present invention relates to a controller device, a communication system and a controlling method for transmitting commands for designating two modes used in a setup including a controller device and a plurality of target devices reserved by the controller device, the devices being interconnected by a data bus for transmitting data in a predetermined communication format, one of the two modes allowing the target devices to communicate with one another, the other mode inhibiting the reserved target devices from thus communicating. More particularly, the invention relates to a communication system and a controlling method for varying between such two modes a standby time that must elapse before a command can be accepted following a bus reset, one mode permitting communication between the reserved target devices, the other mode inhibiting such intercommunication.
Description of the Related Art
Today, the IEEE (Institute of Electrical and Electronic Engineers) 1394 data interface has gained widespread acceptance as a digital data interface. Faster than the SCSI among others in terms of data transfer, the IEEE 1394 data interface is known to permit isochronous communication whereby data of a predetermined size are transmitted and received periodically. As such, the IEEE 1394 data interface is deemed advantageous in transferring stream data such as AV data in real time.
Under these circumstances, data transmission systems have been proposed which interconnect various digital AV (audio visual) devices and electronic equipment such as a personal computer via a data bus complying with digital data interface standards such as the IEEE 1394.
Such AV systems permit so-called remote control. For example, where a disc recording and reproducing apparatus is connected with a personal computer, suitably operating the personal computer can control the disc recording and reproducing apparatus in recording and playback as well as in editing recorded sources.
According to digital data interface standards such as those of the IEEE 1394, the device executing remote control is called a controller and the device placed under remote control is called a target.
Where remote control is provided over AV systems connected through the IEEE 1394 data interface as in the above example, it may happen that one target is subject to remote control by a plurality of controllers or that local keys of the target (e.g., operation keys attached to the device acting as the target) remain effective. Such cases are likely to lead to processing conflicts between the controller(s) and the target or to consequential inconsistencies therebetween.
This applicant already proposed a solution to such irregularities. The proposed solution involved defining reserve commands of a data interface allowing a controller to reserve a target device under remote control (e.g., PCT Application No. PCT/JP99/06411).
Illustratively, when a reserve command sent by a controller to a target is accepted, the target enters a reserve mode. In the reserve mode, the target rejects commands (i.e., rejects communication) from any device other than the controller that has transmitted the reserve command. Processing conflicts conceivable between the controller and the target or possible consequential inconsistencies therebetween are circumvented by inhibiting attempts to operate the target by any device other than the controller.
In practice, however, an AV system establishing a reserve mode can run into some problems. For example, when a player is operated to copy or dub data to a recorder, it is necessary to communicate copy control information or like data regarding copyrights between the player and the recorder. If at least one of the player and the recorder is reserved by another device such as a personal computer, there can be no communication of the copy control information or the like between the player and the recorder, which inhibits copying of the appropriate data.
That is, establishing the reserve mode can disable communication between the target device and any device other than the controller reserving the target when the target needs to carry out an operation with a different device for a given purpose.